Glyphosate, or N-phosphonomethylglycine (HOOCCH.sub.2 NHCH.sub.2 PO(OH).sub.2), is a well-known translocated, postemergence, broadspectrum herbicide. The typical commercial formulation contains about 41% of the isopropylamine salt of glyphosate and is believed to contain about 12% by weight of a tallow amine ethoxylate surfactant. Glyphosate is a relatively insoluble acid, and thus is typically formulated and applied as a salt, such as the isopropylamine, sodium or ammonium salt.
Surfactants are typically incorporated into the formulation to improve the activity of the glyphosate. However, the term "surfactant" is ambiguous, as the form supplied by manufacturers is not necessarily a single compound, but can be a mixture. For example, with ethoxylated surfactants, the degree of ethoxylation can be and typically is a statistical mixture. The literature describes use of surfactants in glyphosate compositions and in particular, Weed Science, Vol. 25, pp 275-287 (1977) demonstrates the necessity of including a surfactant in glyphosate formulations. Conventional glyphosate formulations include the use of surfactants such as silicone to enhance the rainfast properties of glyphosate formulations. However, commercialization of such formulations has been hindered by the cost of incorporation of such surfactants into the formulations, and by the hydrolytic instability of such adjuvants. Other formulations including surfactants are disclosed in U.S. Pat. Nos. 5,362,705, 5,180,414 and 5,118,338.
In addition, in view of the recent environmental concerns surrounding the use of chemical herbicides and the possibility that residuals thereof might contaminate food, ground water, etc., a substantial reduction in the amount of herbicide necessary to be effective would be highly desirable.
It is therefore an object of the present invention to improve the rainfast properties of glyphosate formulations without the use of silicone surfactants.
It is a further object of the present invention to enhance the efficacy of glyphosate formulations in an environmentally friendly manner.